Weekly Vitamins

Q: Can some vitamin and mineral supplements be taken once a week instead of daily?

A: A few can. The body is able to store some vitamins, especially the “fat-soluble” ones like vitamin D, for weeks or even months. The same is true of iron,zinc and some B vitamins, including folic acid. This has been studied mostly in developing countries, where deficiencies are common and once-weekly administration is easier and cheaper.

In this country, research shows that in people with very low blood levels of vitamin D, high once-weekly (or even monthly) doses— such as 8,000 to 50,000 IU of vitamin D a week for six to eight weeks—can raise blood levels as well as comparable daily dosing. Doses at the high end of that range should be used only under a doctor’s supervision.

Similarly, some studies have found that people with anemia due to vitamin B12 deficiency can take very large oral doses of the vitamin once a week or once a month, under medical supervision, instead of B12 injections. And according to a 2009 Cochrane Collaboration review, once-weekly high-dose iron supplements (either alone or with folic acid) may be an option for pregnant women.

Despite the conventional “one-a-day” approach to multivitamin/mineral pills, taking a multi supplying 100 percent of the Daily Values every few days “would be more than adequate” for most people, according to Sharon Fleming, Ph.D., Professor of Nutritional Science and Toxicology at UC Berkeley.

But keep in mind, if your diet is good and you don’t have a known deficiency, you probably don’t need to take any supplement, except perhaps calcium and vitamin D—plus folic acid if you are a woman of child-bearing age, and most likely vitamin B12 if you’re a strict vegetarian.